1. Field of the Invention
The present invention relates to earthquake early warning, and more specifically, to the method of using a neural network to produce a complete earthquake profile prior to the actual arrival of strong ground motion.
2. Description of Related Art
U.S. Pat. No. 5,270,649 is directed to the prediction of earthquakes by measuring a magnetic spin resonance of the earth's crust. When the value of an alarm signal exceeds a threshold value, an alarm is generated. U.S. Pat. No. 4,980,644 is directed to an earthquake predicting magnetometer having a compass assembly with a graduated dial and an adjustably positionable magnet assembly having magnetic poles oriented opposite the direction markings on the compass dial. The patent discloses that when the magnetosphere of the earth weakens prior to a major seismic event, the compass needle will point to the south on a graduated scale of the dial, indicating an imminent quake of large magnitude.
U.S. Pat. No. 4,884,030 relates to a system for acquisition and separation of the effects of simultaneous sources of electromagnetic fields to predict earthquakes. The patent discloses an array of pickups connected to registration means where the minimum number of pickups per array is equal to 2s+2, where s is equal to a number of simultaneous sources to be analyzed. U.S. Pat. No. 4,837,582 is directed to the detection of electromagnetic waves generated by the earth's crust under strain. An antenna is located in the earth to receive preearthquake electromagnetic waves generated prior to the occurrence of an earthquake.
U.S. Pat. No. 4,628,299 discloses a seismic warning system the monitors the ambient broadband radio frequency field strength from broadcast stations. The system indicates a warning if the field strength drops significantly. U.S. Pat. No. 4,612,506 is directed to a method of forecasting earthquakes as a function of transient variations in electric earth currents. U.S. Pat. No. 4,297,690 is directed to an earthquake alarm system that detects lateral impulse movements of structures and generates an audible sound when movement exceeds a limit. U.S. Pat. No. 4,170,776 describes a system for detecting earth crustal deformations using an RF interferometer technique.
It is desirable to use the first seconds of seismic activity from an emerging earthquake to predict the size and duration of the impending S, Rayleigh, and Love waves. These later arriving waves produce both horizontal and vertical ground motion and tend to cause the greatest damage to structures. An accurate prediction of the later arriving energy will provide a complete profile of the impeding earthquake which can include a magnitude prediction, onset time, epicentral distance, earthquake azimuth, and duration of heavy shaking. The system could be implemented in electronic hardware and would be useful as a single station warning system or as an element in a distributed system. The present invention provides such a system.